EP3570369A1

EP3570369A1 - Automobile window glass

Info

Publication number: EP3570369A1
Application number: EP18739175.0A
Authority: EP
Inventors: Tatsumi Tokuda
Original assignee: Nippon Sheet Glass Co Ltd
Current assignee: Nippon Sheet Glass Co Ltd
Priority date: 2017-01-11
Filing date: 2018-01-11
Publication date: 2019-11-20
Also published as: CN110168806A; WO2018131645A1; EP3570369A4; CN114421126A; JP6879744B2; JP2018113591A

Abstract

A vehicle window glass according to the present invention includes a glass plate, a defogger formed on the glass plate and having a pair of bus bars and a plurality of horizontal heating wires that join the pair of bus bars, at least one vertical element provided in the defogger and intersecting at least one of the horizontal heating wires, and a first antenna element formed on the glass plate and capacitively coupled to the defogger, the first antenna element being configured to receive broadcast waves having a frequency range of wavelengths λ₁ to λ₂ that is higher than an FM frequency range, and Pmin<α·λ₁/2 being satisfied, where Pmin is a smallest distance, out of the distance between one of the bus bars and the vertical element and the distance between the vertical antennas, and α is the shortening coefficient of wavelength of the glass plate.

Description

Technical Field

The present invention relates to a vehicle window glass.

Background Art

Devices such as defoggers for removing condensation or ice and antennas for receiving predetermined radio waves may be provided on the surface of a window glass for vehicles (particularly the rear glass) that is to be attached to an automobile. Defoggers have a plurality of horizontal heating wires that extend horizontally across the entirety of the window glass. Also, as antennas, DAB antenna elements for receiving DAB (Digital Audio Broadcasting; hereinafter "DAB") broadcasts may be used, for example, and Patent Literature 1 proposes a window glass for vehicles on which a DAB antenna element is provided together with a defogger.

Citation List

Patent Literature

Patent Literature 1: JP 2014-216805A

Summary of Invention

Technical Problem

However, the inventor of the present invention found that, with a window glass such as described above, problems such as the following occur. That is, the inventor found that, with a window glass such as described above, a problem occurs in that the reception performance of the DAB antenna element decreases, due to radio waves in the frequency band that should be received by the DAB antenna element being excited as standing waves in the horizontal heating wires . The inventor found such a problem occurs not only with DAB antenna elements but also antenna elements that receive broadcast waves having a wavelength band of a higher frequency than FM, such as digital television broadcast waves, for example. The present invention was made in order to solve the above problem, and an object thereof is to provide a vehicle window glass that is, in the case where an antenna element that receives broadcast waves of a higher frequency band than FM is used together with a defogger, able to suppress a decrease in the reception performance of such an antenna element.

Solution to Problem

A vehicle window glass according to the present invention includes a glass plate, a defogger formed on the glass plate and having a pair of bus bars and a plurality of horizontal heating wires that join the pair of bus bars, at least one vertical element provided in the defogger and intersecting at least one of the horizontal heating wires, and a first antenna element formed on the glass plate and capacitively coupled to the defogger, the first antenna element being configured to receive a broadcast wave having a frequency range of wavelengths λ₁ to λ₂ that is higher than an FM frequency range, and Pmin<α·λ₁/2 being satisfied, where Pmin is a smallest distance, out of a distance between one of the bus bars and the vertical element and a distance between the vertical antennas, and α is a shortening coefficient of wavelength of the glass plate.
Note that "horizontal" in the present invention is used to mean a direction generally parallel to the installation surface of the vehicle, and "vertical" refers to a direction generally orthogonal to "horizontal". Accordingly, "horizontal" and "vertical" do not necessarily indicate strict directions, and, for example, what is referred to as "horizontal" may be slightly inclined rather than being strictly parallel to the installation surface of the vehicle. The meanings of "horizontal" and "vertical" are the same throughout this specification.
In the above vehicle window glass, a configuration can be adopted in which Pmax<α·λ₁/2 is satisfied, where Pmax is a largest distance, out of a horizontal distance between one of the bus bars and the vertical element and a horizontal distance between the vertical elements.
In the above vehicle window glass, a configuration can be adopted in which Pmin, α and λ₁ satisfy Pmin≤α·3λ₁/8.
In the above vehicle window glass, a configuration can be adopted in which the vehicle window glass further includes a second antenna element formed on the glass plate and configured to receive a broadcast wave of a higher frequency band than an FM frequency band, the second antenna element being capacitively coupled to the defogger.
In the above vehicle window glass, a configuration can be adopted in which power is supplied to the first antenna element and the second antenna element from a common power supply part.
In the above vehicle window glass, a configuration can be adopted in which the first antenna element and the second antenna element are integrally connected.
In the above vehicle window glass, a configuration can be adopted in which a sum of a distance between the vertical element and a power supply part of the first antenna element and a length of the vertical element is greater than or equal to α·λ₁/4.
In the above vehicle window glass, a configuration can be adopted in which a sum of a distance between the vertical element and a power supply part of the first antenna element and a length of the vertical element is greater than or equal to α·λ₂/4.
In the above vehicle window glass, a configuration can be adopted in which the first antenna element is configured to receive a DAB broadcast wave, and a distance between the first antenna element and the defogger is less than or equal to 15 mm.

Advantageous Effects of Invention

With a vehicle window glass according to the present invention, it is possible, in the case of using an antenna element that receives broadcast waves of a higher frequency band than FM together with a defogger, to suppress a decrease in the reception performance of such an antenna element.

Brief Description of Drawings

FIG. 1 is a front view of a rear glass of an automobile in which an embodiment of a vehicle window glass according to the present invention is mounted.
FIG. 2 is a diagram showing a model of a window glass according to working examples and comparative examples.
FIG. 3 is a graph showing the reception performances of working example 1 and comparative examples 1 and 2.
FIG. 4 is a graph showing the reception performances of working examples 2 and 3 and comparative example 1.
FIG. 5 is a graph showing the reception performances of working examples 3 to 5 and comparative example 1.
FIG. 6 is a plan view showing a window glass according to working example 8.
FIG. 7 is a graph showing the reception performance in a DAB frequency range of working examples 6 to 12 and comparative example 1.
FIG. 8 is a diagram showing current distribution on a defogger of working example 6.
FIG. 9 is a diagram showing current distribution on a defogger of working example 7.
FIG. 10 is a diagram showing current distribution on a defogger of working example 8.
FIG. 11 is a diagram showing current distribution on a defogger of working example 9.
FIG. 12 is a diagram showing current distribution on a defogger of working example 10.
FIG. 13 is a diagram showing current distribution on a defogger of working example 11.
FIG. 14 is a diagram showing current distribution on a defogger of working example 12.
FIG. 15 is a graph showing the reception performance in a DAB frequency range of working examples 13 to 17 and comparative example 1.

Description of Embodiments

Hereinafter, an embodiment of a vehicle window glass according to the present invention will be described, with reference to the drawings. FIG. 1 is a front view of a rear glass of an automobile to which the vehicle window glass according to the present embodiment is applied. Note that, hereinafter, for convenience of description, the up-down direction in FIG. 1 may be referred to as the up-down direction or the vertical direction, and the left-right direction in FIG. 1 may be referred to as the left-right direction or the horizontal direction, based on the orientation of FIG. 1, but this orientation is not intended to limit the invention.

1. Vehicle Window Glass

As shown in FIG. 1, with the vehicle window glass according to the present embodiment, a defogger 2 and an FM/DAB shared antenna element 3 (hereinafter, simply "antenna element") are mounted on a glass plate 1. Hereinafter, these members will be described in order.

1-1. Glass Plate

A well-known glass plate for automobiles can be utilized for the glass plate 1. For example, heat absorbing glass, common clear glass, common green glass or UV green glass may be utilized as the glass plate 1. Such a glass plate 1 needs, however, to realize a visible light transmittance in line with safety standards of the country in which the automobile will be used. For example, solar absorbance, visible light transmittance and the like can be adjusted to meet safety standards. Hereinafter, an example of the composition of clear glass and an example of the composition of heat absorbing glass will be shown.

Clear Glass

SiO₂: 70 to 73 mass%
Al₂O₃: 0.6 to 2.4 mass%
CaO: 7 to 12 mass%
MgO: 1.0 to 4.5 mass%
R₂O: 13 to 15 mass% (R is an alkaline metal)
Total iron oxide in terms of Fe₂O₃ (T-Fe₂O₃): 0.08 to 0.14 mass%

Heat Absorbing Glass

The composition of heat absorbing glass can, for example, be given as a composition, based on the composition of clear glass, including total iron oxide in terms of Fe₂O₃ (T-Fe₂O₃) at a ratio of 0.4 to 1.3 mass%, CeO₂ at a ratio of 0 to 2 mass%, and TiO₂ at a ratio of 0 to 0.5 mass%, and in which the skeletal component (mainly SiO₂ or Al₂O₃) of the glass is reduced by an amount equivalent to the increase in T-Fe₂O₃, CeO₂ and TiO₂.
Note that the type of glass plate 1 is not limited to clear glass or heat absorbing glass, and is selectable as appropriate according to the embodiment. For example, the glass plate 1 may be a resin window made of acrylic resin, polycarbonate resin or the like.
Also, such a glass plate 1, apart from being constituted by a single glass plate, may be a laminated glass in which an intermediate film such as a resin film is sandwiched by a plurality of plates of glass. Note that the shortening coefficient of wavelength α of a glass plate also changes depending on factors such as the thickness of the glass plate, and is, for example, approximately 0.7 in the case where a defogger, an antenna element and the like are formed on a single glass plate, and approximately 0.5 in the case of a laminated glass in which an intermediate film is sandwiched by two glass plates.

1-2. Defogger

Next, the defogger 2 will be described. As shown in FIG. 1, the defogger 2 is disposed in the vicinity of the middle of the glass plate 1 in the vertical direction, and is formed so as to extend across the entirety of the glass plate 1 in the left-right direction. Specifically, this defogger 2 includes a pair of bus bars 21a and 21b for power supply that extend in the up-down direction along both side edges of the glass plate 1. Here, for convenience of description, the bus bar on the left side will be referred to as a first bus bar 21a and the bus bar on the right side will be referred to as a second bus bar 21b. Between both bus bars 21a and 21b, a plurality of horizontal elements (horizontal heating wires) 22 are disposed in parallel at a predetermined interval, and heat for defogging is produced by power supply from the bus bars 21a and 21b. Also, two vertical elements 41 and 42 that extend in the up-down direction are formed in this defogger 2. Here, for convenience of description, the vertical element on the left side will be referred to as a first vertical element 41, and the vertical element on the right side will be referred to as a second vertical element 42. These vertical elements 41 and 42 extend so as to link the horizontal element that is uppermost (hereinafter, uppermost horizontal element) 221 and the horizontal element that is lowermost (hereinafter, lowermost horizontal element) 222, so as to intersect all the horizontal elements 22.

1-2-1. Disposition of Vertical Elements

Incidentally, standing waves constantly occur in the defogger 2, and the wavelength band of these standing waves depends on the length of the horizontal elements 22 of the defogger 2. Also, in the case where the antenna element 3 discussed later is disposed near the defogger 2 and this antenna element 3 is capacitively coupled or directly coupled to the defogger 2, the inventor found that, if the length of the horizontal elements 22 is half the wavelength λ of broadcast waves that are received by the antenna element 3, or in other words, an integer multiple of λ/2, the antenna element 3 is affected by the standing waves that occur in the defogger 2 (note that λ as referred to here is obtained by multiplying the wavelength by the shortening coefficient of wavelength of the glass plate). That is, if radio waves received with the defogger 2 are excited in the defogger 2 as standing waves of half the frequency band of the antenna element 3, energy of an amount equal to the resultant excitation energy is supplied from the defogger 2 to the antenna element through capacitive coupling or direct coupling, and the radio waves of the frequency band of the antenna element 3 are trapped in the defogger 2. As a result, it was noted that the reception sensitivity of the antenna element 3 decreases. It was also noted, however, that in the case where the horizontal elements 22 are divided by the vertical elements 41 and 42, as in the present embodiment, the stationary waves can be controlled depending on the length of the divided horizontal elements, or in other words, the intervals of the bus bars 21a and 21b and the vertical elements 41 and 42, and the interval between the adjacent vertical elements 41 and 42, and, as a result, the decrease in the reception sensitivity of the antenna element 3 can be suppressed.
Also, when standing waves occur and an integer multiple of the frequency thereof corresponds to the frequency band of the antenna element 3, reception performance as an antenna decreases and the antenna element 3 no longer functions adequately. However, as mentioned above, a decrease in reception performance can be prevented by adjusting the intervals of the bus bars 21a and 21b and the vertical elements 41 and 42 and the interval between the adjacent vertical elements 41 and 42 to control the frequency of the standing waves . Hereinafter, this point will be considered.
Here, the interval of the first bus bar 21a and the first vertical element 42 in the horizontal direction will be referred to as a first interval P1, the interval of both vertical elements 41 and 42 in the horizontal direction will be referred to as a second interval P2, and the interval of the second vertical element 42 and the second bus bar 21b in the horizontal direction will be referred to as a third interval P3. Note that these intervals P are the intervals of lower end parts thereof.
The vertical elements 41 and 42 are disposed so as to satisfy any of the following equations (1) to (3), where Pmin and Pmax are respectively the smallest and largest of these three intervals, λ₁ to λ₂ are the wavelength bands of DAB broadcast waves that are received by the antenna element 3, and α is the shortening coefficient of wavelength of the abovementioned glass plate 1. $Pmin < α \cdot λ_{1} / 2$
$Pmax < α \cdot λ_{1} / 2$
$Pmin \leq α \cdot 3 λ_{1} / 8$
Note that the wavelength band corresponding to 170 to 240 MHz, which is the frequency range of DAB Band III, will be approximately 813 to 1147 mm (= αλ₁ to αλ₂) when the shortening coefficient of wavelength of a typical glass plate is taken into consideration (where α = 0.65).
Equation (1) shows that the smallest interval Pmin, among the intervals of the divided horizontal elements, is smaller than α·λ₁/2. Accordingly, at least one interval is smaller than α·λ₁/2, among the plurality of intervals, and the decrease in the reception performance of the antenna element due to standing waves is thereby suppressed. Equation (2) shows that the largest interval Pmax, among the intervals of the divided horizontal elements, is smaller than α·λ₁/2. Accordingly, all the intervals are smaller than α·λ₁/2, and a decrease in the reception performance of the antenna element due to standing waves is thereby suppressed. That is, an improvement in the reception performance becomes further possible over disposition of the vertical elements in equation (1).
Also, equation (3) shows that the smallest interval Pmin, among the intervals of the divided horizontal elements, is less than α·3λ₁/8. With this equation (3), even though the smallest interval Pmin is being considered, since this interval is considerably lower than α·λ₁/2, a decrease in the reception performance of the antenna element due to standing waves is thereby suppressed.
Note that, in the above equations (1) to (3), DAB broadcast waves are mainly taken into consideration, and FM broadcast waves are not taken into consideration. The reasons for this are as follows. The frequency of FM broadcast waves is 76 to 108 MHz (corresponding wavelengths are λ₃ to λ₄), and the wavelength with consideration for the shortening coefficient of wavelength α is approximately 1806 to 2766 mm (= αλ₃ to αλ₄). In contrast, the horizontal elements of a typical vehicle are divided at about 0.5 m when one vertical element is provided in the vicinity of the center of the defogger, for example, and is thus considerably shorter than the half wavelength αλ/2 of FM broadcast waves. Accordingly, the reception performance of FM broadcast waves tends not to be affected by the standing waves when at least one vertical element is provided. In contrast, the wavelength of DAB broadcast waves is, as mentioned above, approximately 813 to 1147 mm, and thus reception performance tends to be affected by the standing waves. Accordingly, in the present embodiment, the vertical elements 41 and 42 are provided with consideration for the above interval P, mainly with the object of improving the reception performance of DAB broadcast waves.

1-2-2. Length of the Vertical Elements

Next, a length L of the vertical elements 41 and 42 will be considered. The length L of the vertical elements 41 and 42 and a length D from a power supply part 31 to the vertical elements 41 and 42 in the up-down direction are preferably provided so as to satisfy the following equations (4) and (5) . $L + D \geq α \cdot λ_{1} / 4$
$L + D \geq α \cdot λ_{2} / 4$
Since the effective height of the antenna increases when the length of the vertical elements becomes longer so as to satisfy equation (4), reception performance can be improved. Reception performance can be further improved when equation (5) is satisfied.

1-3. Antenna Element

Next, the antenna element 3 will be described. The antenna element 3 according to the present embodiment is, as mentioned above, used as both an FM antenna and a DAB antenna. Specifically, the antenna element 3 is configured as follows. First, this antenna element 3 is, in the glass plate 1, disposed upward of the defogger 2, and is provided with the power supply part 31 disposed to the left of the middle of the upper end edge of the glass plate 1. The antenna element 3 is provided with a first vertical part 32 that extends downward from this power supply part 31, and a first horizontal part 33 that extends right-left in the horizontal direction from the lower end of this first vertical part 32, and DAB broadcast waves are mainly received with the first vertical part 32 and the first horizontal part 33. Furthermore, this antenna element 3 has a substantially J-shaped region provided with a second horizontal part 34 that extends toward the left side from partway along the first vertical part 32, a second vertical part 35 that extends downward from the left end of this second horizontal part 34, and a third horizontal part 36 that extends toward the right side from the lower end of the second vertical part 35, and FM broadcast waves are mainly received with this region. Note that the first horizontal part 33 and the third horizontal part 36 are disposed with an interval therebetween in the horizontal direction, and are disposed in substantially the same position in the up-down direction.
The first horizontal part 33 and the third horizontal part 36 are respectively disposed at a predetermined interval S from the uppermost horizontal element 221 of the defogger 2. At this time, the interval S between the first horizontal part 33 and the uppermost horizontal element 221 is preferably 15 mm or less, and, in particular, is preferably 10 to 15 mm. Since the antenna element 3 and the defogger 2 are capacitively coupled, and the defogger 2 is also utilized as an antenna, reception performance thereby improves.
Also, the power supply part of the above antenna element 3 is respectively connected to an FM tuner and a DAB tuner (illustration omitted) via a lead or the like. An amplifier may be inserted upstream of the tuners. Adopting this configuration enables cost reduction. Also, since a DAB/FM antenna is used, the installation area of the antenna element 3 can be reduced.

1-4. Material

A defogger 2 and antenna element 3 such as described above can be formed by laminating a conductive material having conductivity on the surface of the glass plate 1, such that a predetermined linear pattern is formed. Such a material need only have conductivity, and is selectable as appropriate according to the embodiment, with silver, gold, platinum and the like given as examples. These members can be formed by, for example, printing and baking a conductive silver paste containing silver powder, glass frit and the like on the surface of the glass plate 1.

1-5. Manufacturing Method

Next, a manufacturing method of the window glass according to the present embodiment will be described. The glass plate 1 of the window glass according to the present embodiment can be shaped by methods such as a press-molding method for shaping the glass plate 1 with a press or a self-weight bending method for bending the glass plate 1 under its own weight.
Here, at the time of shaping the glass plate 1 with these respective methods, the glass plate 1 is heated to the vicinity of the softening point in a heating furnace. Before being placed in this heating furnace, the glass plate 1 is flat in shape, and a paste for the various materials mentioned above, such as a silver paste, for example, is printed on the surface of this glass plate 1. Then, by placing the glass plate 1 in the heating furnace, the silver paste printed on the glass plate 1 is baked together with shaping the glass plate 1, enabling the defogger 2 and the antenna element 3 to be formed.

2. Features

As mentioned above, in the present embodiment, by adjusting the intervals of the bus bars 21a and 21b and the vertical elements 41 and 42 of the defogger 2 and the interval between the vertical elements 41 and 42, the influence of the standing waves that occur in the defogger 2 can be reduced, and a decrease in the reception performance of the antenna element 3 can be suppressed.

3. Variations

Although an embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various changes can be made without departing from the gist of the invention. Note that the following variations can be combined as appropriate.

3-1

Although two vertical elements 41 and 42 are provided in the defogger 2 of the above embodiment, the number of vertical elements is not particularly limited, as long as any of the abovementioned equations (1) to (3) is satisfied. The length of a vertical element is also not particularly limited, and the lengths of the plurality of vertical elements may differ.

3-2

In the above embodiment, although one antenna element 3 is provided, the configuration of the antenna element is not particularly limited. For example, in the above embodiment, an antenna element for both FM and DAB is used, but separate antennas may be provided. Also, an antenna that receives AM or digital television broadcast waves can be provided. In particular, since digital television broadcast waves have a short wavelength, similar to DAB broadcast waves, a decrease in reception performance due to the influence of the standing waves can be suppressed, if the vertical elements are disposed so as to satisfy the above equations (1) to (5), with consideration for the wavelength band thereof. Also, in terms of the object of the present invention, only a DAB or digital television antenna that tends to be affected by standing waves may be provided.
Also, the shape of the antenna element is not particularly limited, and various shapes are possible. To perform capacitive coupling with the defogger 2, however, horizontal parts that extend along the defogger are preferably provided. Furthermore, the antenna element 3 is not particularly limited in terms of position, and may be disposed on the lower side of the defogger 2. Also, the antenna element 3 may be directly coupled to the defogger 2.
For example, in a sedan type vehicle, the reception performance of the antenna element 3 tends to be affected by the trunk or the rear tray, since the attachment angle of the rear glass approaches horizontal. Accordingly, with a sedan type vehicle, the antenna element 3 is preferably provided upward of the defogger 2. On the other hand, in the case where the attachment angle of the glass approaches vertical, as with a hatchback type vehicle, the reception performance is little affected, since there are no metal portions such as the trunk of a sedan type vehicle. Accordingly, in this case, the antenna element 3 may be provided downward of the defogger 2.

3-3

In the above embodiment, an example was shown in which the window glass according to the present invention is applied to the rear glass of an automobile, but this window glass can also be applied to glass other than the rear glass.

Working Examples

Hereinafter, working examples of the present invention will be described. The present invention is, however, not limited to the following working examples.

1. Consideration of Divided Length of Horizontal Elements

As described above, the horizontal elements of the defogger are divided by vertical elements. The inventor found that the standing waves that occur in a defogger affect the reception performance of the antenna element, depending on the length of the divided horizontal elements. In view of this, hereinafter, the relationship between the length of the divided horizontal elements and the reception performance will be considered.
Here, using the model shown in FIG. 2, vertical elements were disposed as appropriate with respect thereto, and the reception performance when the number and position of the vertical elements were changed was calculated. The unit of measurement in FIG. 2 is millimeters (mm). The reception performance in FM (76 to 108 MHz) and DAB band 3 (174 to 240 MHz) was then calculated using three dimensional electromagnetic field simulation software (software for 3D time-area simulation of electromagnetic fields). In this simulation, the glass plate was modeled, assuming typical tempered glass having a thickness of 3.1 mm. Also, the line width of the defogger and the antenna element was set at 1 mm, and the shortening coefficient of the glass plate was set at 0.65. As the simulation procedure, simulation was executed, after having (1) modeled the vehicle, dielectric body, antenna and the like and set the material, and (2) set an appropriate mesh for the vehicle, dielectric body, antenna and the like. Setting and execution of such simulation are common to consideration of all the working examples and comparative examples shown below.
Also, hereinafter, a numerical value obtained by multiplying the wavelength by the shortening coefficient will be referred to as a shortening wavelength. Shortening wavelengths αλ₁ to αλ₂ corresponding to the DAB frequency range are 813 to 1147 mm, and, therefore, shortening half wavelengths αλ₁/2 to αλ₂/2 are 406 to 574 mm. Also, shortening wavelengths αλ₃ to αλ₄ corresponding to the FM frequency range are 1806 to 2566 mm, and, therefore, shortening half wavelengths αλ₃/2 to αλ₄/2 are 903 to 1283 mm.

The number and position of the vertical elements were set as follows. Hereinafter, the horizontal center position of the defogger is given as 0, and the positions of the first bus bar on the left side and the second bus bar on the right side are respectively defined as -465mm and +465 mm. Also, the vertical elements are disposed between the uppermost horizontal element and the lowermost horizontal element. Note that the length of the divided horizontal element is the interval P described in the above embodiment, and, hereinafter, may thus be simply described as "interval P".

Table 1

	Num of Vert. Elements	Position of Vert. Elements							Length of Divided Horiz. Elements (mm)
Comp. Ex. 1	0	-465						465			930
Comp. Ex. 2	1	-465			0			465		465			465
Working Ex. 1	2	-465	-210				210	465	255		420			255
Working Ex. 2	4	-465	-390	-270		270	390	465	75	120	540		120	75
Working Ex. 3	4	-465	-390	-164		164	390	465	75	226	328		226	75
Working Ex. 4	3	-465	-270		0		270	465	195	270			270	195
Working Ex. 5	5	-465	-330	-270	0	270	330	465	135	60	270	270	60	135

Also, the following Table 2 shows the average value and minimum value of the reception performance in the FM frequency range and the frequency range of DAB band 3 in the above working examples 1 to 5 and comparative examples.

Table 2

	FM		DAB
	Avg.	Min. Value	Avg.	Max. Value
Comp. Ex. 1	-21.5	-26.1	-15.1	-26.2
Comp. Ex. 2	-12.4	-15.2	-16.9	-27.8
Working Ex. 1	-11.6	-15.3	-17.0	-23.9
Working Ex. 2	-11.7	-15.5	-14.6	-22.9
Working Ex. 3	-11.6	-15.6	-12.4	-15.4
Working Ex. 4	-11.4	-15.4	-14.0	-16.5
Working Ex. 5	-11.4	-15.5	-11.9	-15.2

First, working example 1 and comparative examples 1 and 2 will be considered. FIG. 3 is a graph showing the relationship between the frequencies and reception performance thereof. As shown in FIG. 3, the reception performances of working example 1 and comparative example 2 in the FM frequency range are generally the same, and are favorable. On the other hand, comparative example 1 has a low reception performance. This is conceivably because, with comparative example 1, the length (interval P) of the divided horizontal elements is 930 mm, and falls within the range (903 to 1283 mm) of the shortening half wavelengths αλ₃/2 to αλ₄/2 corresponding to the FM frequency range. Accordingly, the reception performance is greatly affected by the standing waves.
On the other hand, in the DAB frequency range, the interval P of comparative example 1 is larger than the shortening half wavelengths αλ₁/2 to αλ₂/2 (406 to 574 mm) corresponding to the DAB frequency range. Also, the two intervals P in comparative example 2 both fall in the range of the shortening half wavelengths αλ₁/2 to αλ₂/2 (406 to 574 mm) . Accordingly, comparative examples 1 and 2 both do not satisfy the abovementioned equation (1), and have low reception performances. In particular, the decrease in reception performance near 200 MHz is marked. On the other hand, in working example 1, although one of the three intervals P falls in the range of the shortening half wavelengths αλ₁/2 to αλ₂/2 (406 to 574 mm), the other two intervals P are smaller than this range. Accordingly, working example 1 satisfies the abovementioned equation (1). As a result, the minimum value of reception performance is, as shown in Table 2, higher than comparative examples 1 and 2.
Next, working examples 2 and 3 will be considered. In both of these working examples 2 and 3, the number of vertical elements is four, but the interval P differs. That is, in working example 2, only one (540 mm) of the four intervals P falls in the range of the above shortening half wavelengths αλ₁/2 to αλ₂/2 (406 to 574 mm). On the other hand, all the four intervals P of working example 3 are lower than the range of the above shortening half wavelengths αλ₁/2 to αλ₂/2 (406 to 574 mm). Accordingly, working example 2 satisfies the above equation (1), and working example 3 satisfies the above equation (2).
The results are as shown in FIG. 4. As shown in this diagram, it is noted that working examples 2 and 3 have the same reception performance in the FM frequency range, but that, in the DAB frequency range, working example 2 has a decreased reception performance in a frequency range of approximately 180 MHz and below. On the other hand, working example 3 exhibits a high reception performance across the entire DAB frequency range. Also, the reception performance in both frequency ranges is generally higher than comparative example 1.
Next, working examples 4 and 5 will be considered together with the abovementioned working example 3. These working examples 4 to 6 have different numbers of vertical elements. That is, in working example 4, the number of vertical elements is three, and the four intervals P satisfy the above equation (3). In working example 3, the number of vertical elements is four, and the five intervals P satisfy the above equation (2). Also, in working example 5, the number of vertical elements is five, and the six intervals P satisfy the above equation (3). The results are as shown in FIG. 5.
As shown in this diagram and in Table 2, both of these working examples satisfy equation (1) and equation (2), and reception performance improves as that the number of vertical elements increases. For example, working example 3 satisfies equation (2) and does not satisfy equation (3), but the reception performance is generally higher than working example 4 that satisfies equation (3). Accordingly, it is noted that, as long as at least equation (2) is satisfied, the reception performance improves as the number of vertical elements increases.

2. Consideration of Vertical Element Length

Next, the length of the vertical elements will be considered. Below, working examples 6 to 12 were prepared. These working examples all had four vertical elements, and the interval P was 135 mm, 164 mm, 330 m, 164 mm and 135 mm from the left. As shown in the following Table 3, the length L of the vertical elements was configured differently. Note that lengths D from the power supply part to the vertical elements in the up-down direction were all 100 mm. Also, with regard to equation (4) and equation (5) related to the length of the vertical elements, L+D≥α ·λ₁/4 (203 mm) and L+D≥α·λ₂/4 (287 mm), respectively.

Table 3

	Vert. Element Length L + Up-Down Length D from Power Supply Part to Vert. Elements (mm)	Num of Intersecting Horiz. Elements
Working Ex. 6	53.6+100=153.6	2
Working Ex. 7	80.4+100=180.4	3
Working Ex. 8	107.2+100=207.2	4
Working Ex. 9	134+100=234	5
Working Ex. 10	160.8+100=260.8	6
Working Ex. 11	241.2+100=341.2	9
Working Ex. 12	321.6+100=421.6	12

The vertical elements are configured to extend downward starting from the uppermost horizontal element, and the number of intersecting horizontal elements in Table 2 shows the number of the horizontal elements not including the uppermost horizontal element. For example, FIG. 6 represents working example 8 (dimensions are as shown in FIG. 2, and are the same except for the vertical elements). Working examples 6 to 12 all satisfy equation (2) with regard to the interval P, and working examples 6 and 7 do not satisfy equations (4) and (5) relating to the length of the vertical elements. On the other hand, working examples 8 to 12 satisfy the above equation (4), and working examples 11 and 12 satisfies equation (5).

With regard to the above working examples 6 to 12, the reception performance in the DAB frequency range was calculated as shown in FIG. 7. Note that comparative example 1 in which the length of the vertical elements is 0 m (vertical elements are not provided) is also shown as a reference in FIG. 7. Also, the average value and minimum value of reception performance in the frequency range of DAB band III in working examples 6 to 12 are shown in the following Table 4.

Table 4

	DAB
	Avg.	Min. Value
Comp. Ex. 1	-15.1	-26.2
Working Ex. 6	-13.4	-19.9
Working Ex. 7	-13.0	-17.0
Working Ex. 8	-12.5	-17.5
Working Ex. 9	-12.0	-19.3
Working Ex. 10	-12.1	-17.9
Working Ex. 11	-12.6	-15.8
Working Ex. 12	-12.4	-15.4

As shown in FIG. 7, in the DAB frequency range, working examples 6 to 12 all obtain a high reception performance compared with comparative example 1, and do not have a frequency range in which reception performance is markedly low like comparative example 1. Of these working examples, there is no dip in reception performance across the entire DAB frequency range, if, like working examples 11 and 12, the length of L+D is greater than or equal to αλ₁/4 (203 mm), which satisfies equation (4). Of these, working example 12 has an L+D length greater than or equal to αλ₂/4 (287 mm), which satisfies equation (5), and a frequency range in which the reception performance is particularly high.
Next, the current distribution on the defoggers in working examples 6 to 12 will be described, with reference to FIGS. 8 to 14. FIGS. 8 to 14 are diagrams in which the current distributions on the defoggers in working examples 6 to 12 are color coded. The frequency is 195 MHz. In these diagrams, the areas enclosed by dotted lines show the distribution of current in a range of generally -60 to -30 dB, and the other areas show the distribution of current in a range of generally -30 to 0 dB (the areas are shown with dotted lines since the color coding is difficult to see).
As shown in FIGS. 8 to 14, the number of areas enclosed by dotted lines on the defogger increases from working example 6 to working example 12. In particular, the number of areas in which the current value is low increases in the horizontal elements, and the occurrence of standing waves is suppressed. For example, with working example 12 shown in FIG. 14, it is noted that the current value is low in the horizontal elements of the majority of areas, and the occurrence of standing waves is further suppressed.
On the other hand, with regard to the vertical elements, although a little difficult to see, the current value of the vertical elements increases from working example 6 to working example 12. Accordingly, reception performance increases. The above points are in agreement with the abovementioned results of FIG. 7.

3. Consideration of Distance between Antenna Element and Defogger

Next, the distance between the antenna element and the defogger will be considered. Below, working examples 13 to 17 were prepared. All of these working examples had four vertical elements, and the interval P was 75 mm, 226 mm, 328 m, 226 mm and 75 mm from the left. Also, as shown in the following Table 5, a distance S from the first horizontal part and third horizontal part of the antenna element to the uppermost horizontal element was configured differently. Note that working example 13 has a distance S is 0 mm, and thus the antenna element and the defogger are directly coupled. Table 5

Distance S(mm)

Working Ex. 13 0

Working Ex. 14 5

Working Ex. 15 10

Working Ex. 16 15

Working Ex. 17 20

With regard to the above working examples 13 to 17, the reception performance in the DAB frequency range was calculated as shown in FIG. 15. In FIG. 15, comparative example 1 is also shown for reference. Also, the average value and minimum value of reception performance in the frequency range of DAB band III in working examples 13 to 17 are shown in the following Table 6.

Table 6

	DAB
	Avg.	Min. Value
Comp. Ex. 1	-15.1	-26.2
Working Ex. 13	-11.1	-15.2
Working Ex. 14	-11.4	-15.5
Working Ex. 15	-12.4	-16.9
Working Ex. 16	-12.6	-17.2
Working Ex. 17	-15.5	-22.3

As shown in FIG. 15, in the DAB frequency range, working examples 13 to 17 all obtain a high reception performance compared with comparative example 1, and do not have a frequency range in which reception performance is markedly low like comparative example 1. Of these working examples, there is no dip in reception performance across the entire DAB frequency range, when, like working examples 13 to 16, the distance S is less than or equal to 15 mm.

Reference Signs List

1: Glass plate
2: Defogger
21a: Bus bar
21b: Bus bar
22: Horizontal element (horizontal heating wire)
3: Antenna element
41, 42:: Vertical element

Claims

A vehicle window glass comprising:
a glass plate;

a defogger formed on the glass plate and having a pair of bus bars and a plurality of horizontal heating wires that join the pair of bus bars;

at least one vertical element provided in the defogger and intersecting at least one of the horizontal heating wires; and

a first antenna element formed on the glass plate and capacitively coupled or directly coupled to the defogger,

wherein the first antenna element is configured to receive a broadcast wave having a frequency range of wavelengths λ₁ to λ₂ that is higher than an FM frequency range, and

Pmin<α·λ₁/2 is satisfied, where Pmin is a smallest distance, out of a distance between one of the bus bars and the vertical element and a distance between the vertical antennas, and α is a shortening coefficient of wavelength of the glass plate.
The vehicle window glass according to claim 1,
wherein Pmax<α·λ₁/2 is satisfied, where Pmax is a largest distance, out of a horizontal distance between one of the bus bars and the vertical element and a horizontal distance between the vertical elements.
The vehicle window glass according to claim 1,
wherein Pmin, α and λ₁ satisfy Pmin≤α·3λ₁/8.
The vehicle window glass according to any of claims 1 to 3, further comprising:
a second antenna element formed on the glass plate and configured to receive a broadcast wave of a higher frequency band than an FM frequency band,

wherein the second antenna element is capacitively coupled to the defogger.
The vehicle window glass according to claim 4,
wherein power is supplied to the first antenna element and the second antenna element from a common power supply part.
The vehicle window glass according to claim 5,
wherein the first antenna element and the second antenna element are integrally connected.
The vehicle window glass according to any of claims 1 to 6,
wherein a sum of a distance between the vertical element and a power supply part of the first antenna element and a length of the vertical element is greater than or equal to α·λ₁/4.
The vehicle window glass according to any of claims 1 to 6,
wherein a sum of a distance between the vertical element and a power supply part of the first antenna element and a length of the vertical element is greater than or equal to α·λ₂/4.
The vehicle window glass according to any of claims 1 to 8,
wherein the first antenna element is configured to receive a DAB broadcast wave, and
a distance between the first antenna element and the defogger is less than or equal to 15 mm.